1. Field of the Invention
The present invention relates to a ballast cleaning machine for cleaning a ballast bed supporting a track, which comprises a machine frame extending in a longitudinal direction and supported on the track by undercarriages for movement in an operating direction, two vertically and laterally adjustable endless ballast excavating chains sequentially arranged in the longitudinal direction for excavating ballast from the ballast bed, a first one of the endless ballast excavating chains leading a second one of the endless ballast excavating chains in the operating direction, and a track lifting device mounted on the machine frame. Conveyor arrangements are provided for conveying the excavated ballast to a screening installation for cleaning ballast, and for distributing the cleaned ballast to the ballast bed.
2. Description of the Prior Art
Ballast cleaning machines of this type have been disclosed in published German paent application No. 43 43 148 A1, French patent No. 1,029,167 and German Democratic Republic patent No. 240 043. These machines have a machine frame supported on undercarriages at the ends of the machine frame for movement on the track in an operating direction, and two excavating chains are mounted on the machine frame immediately following each other in the operating direction. A ballast cleaning screening installation is arranged between the two ballast excavating chains. While the machine continuously advances along the track, the first excavating chain, as seen in the operating direction, excavates the ballast and conveys it to the screening installation, and the second, trailing excavating chain removes the soil underlying the ballast bed. The removed soil is conveyed to trailing storage cars. Before the cleaned ballast is distributed from the screening installation, a protective sand layer is laid on the subgrade.
French patent No. 714,645 shows an arrangement of four endless bucket chains for raising excavated ballast and convey it to a screening installation.
Another machine for rehabilitating a ballast bed is disclosed in European patent application No. 0 629 744 B1. A first excavating chain excavates a layer of ballast, and the excavated ballast is comminuted in a stone crusher. The comminuted ballast is distributed on the excavated ballast bed and compacted to serve as a protective layer over the subgrade. A second excavating chain mounted on a second machine frame removes soil, which is replaced by the protective layer, whereupon the track is laid. In a subsequent operating stage, new ballast is introduced to provide a ballast bed.
It is the primary object of this invention to provide a ballast cleaning machine of the first-described type, which achieves a particularly high ballast cleaning efficiency with two endless ballast excavating chains which encompass the track.
The above and other objects are accomplished in accordance with the invention with a ballast cleaning machine for cleaning the ballast bed supporting a track, which comprises a machine frame extending in a longitudinal direction and supported on the track by undercarriages for movement in an operating direction. Two vertically and laterally adjustable endless ballast excavating chains are sequentially arranged in the longitudinal direction for excavating ballast from the ballast bed, a first one of the endless ballast excavating chains leading a second one of the endless ballast excavating chains in the operating direction. A track lifting device is mounted on the machine frame, a first conveyor arrangement conveys the ballast excavated by the first endless ballast excavating chain to a first screening installation for cleaning ballast, the first conveyor arrangement having an input end arranged to receive the excavated ballast from the first endless ballast excavating chain and an output end arranged to discharge the conveyed excavated ballast into the first screening installation, a second conveyor arrangement conveys the ballast excavated by the second endless ballast excavating chain to a second screening installation, the second conveyor arrangement having an input end arranged to receive the excavated ballast from the second endless ballast excavating chain and an output end arranged to discharge the conveyed excavated ballast into the second screening installation, and a third conveyor arrangement distributes the cleaned ballast to the ballast bed.
A machine combining these features substantially enhances the ballast excavating capacity in a ballast cleaning operation so that very large screening installations may be used for cleaning the large volume of excavated ballast. By providing two separate screening installations at respective ends of the machine, optimal adaptation to different capacities of the two endless ballast excavating chains may be obtained. In the case of a badly encrusted ballast bed section, for example, the ballast cleaning operation may be readily optimized by subjecting a first ballast bed section which is relatively clean to a normal cleaning on the first screening installation while the heavily encrusted or dirty ballast bed section is subjected to intensive cleaning on a specially designed second screening installation.